Side impact airbag systems for use in motor vehicles have been adopted to mitigate occupant injuries during motor vehicle side impact events, and are generally well-known in the art. Traditionally, such side impact airbag systems have been used in combination with exterior motor vehicle components to manage and control motor vehicle impact events with external objects during side impact events. Further, side impact airbag systems are used to address vehicle intrusion during a side impact event and provide occupant restraint against occupant collision with interior motor vehicle components, such as the so-called A-pillar, B-pillar, door trim, and interior upper rail assembly. Side airbag systems are designed to deploy substantially immediately (i.e., 5 to 10 milliseconds) upon detection of the high speed impact event and stay inflated for about 30 to 70 milliseconds.
In the United States, Federal Motor Vehicle Safety Standard (FMVSS) No. 214 was promulgated to address side impact events. In sum, FMVSS 214 presently requires that a simulated vehicle occupant experience upper and lower thoracic loads and head de-accelerations within specified limits. However, the complexity of side impact mitigation has increased significantly with the introduction of new requirements for FMVSS 214 and the new Lateral Impact New Car Assessment Program (LINCAP). Also, motor vehicles are tested according to side impact procedures and criteria established by the Insurance Institute for Highway Safety (IIHS). Additionally, various side impact procedures and criteria are emerging worldwide, for example, with the introduction of the European New Car Assessment Program (EuroNCAP) and Chinese New Car Assessment Program (C-NCAP). While all of these evaluative techniques share the same goal of improving side impact crashworthiness, not all share the same procedures and criteria.
Yet motor vehicle design and engineering efforts in the face of a global market encourages the use of common solutions. One solution to side impacts is the use of a side impact airbag. Yet a common side impact airbag solution for a global market requires that the side airbag perform within the established criteria of every market, and obtain crashworthiness results that fall within the criteria of the United States (UNCAP), Europe (EuroNCAP) and China (C-NCAP), as well as IIHS testing. It is possible to use a different side impact airbag for each market, for example, one side impact airbag for use in the United States market and a different side impact airbag for the rest of the global market. However, this does not provide a common solution worldwide.
Further, side impact mitigation requires accommodation of a wide range of occupant sizes and masses. For example, it may be desirable to design the side impact airbag to be relatively “soft” in order to accommodate a more vulnerable prototypical occupant, such as the so-called 5th percentile occupant. However, such a side impact airbag may be too “soft” for other prototypical occupant profiles, such as for the 50th percentile occupant.
Finally, it has also been observed that a typical side impact airbag, when deployed, may not engage the entire occupant's body side because the occupant's upper arm prevents the side airbag from engaging the entire thoracic region of the body at early stages of impact. Hence, solutions for providing side impact occupant protection with a common global design would be advantageous.
The vehicle side airbag disclosed herein particularly accomplishes the foregoing optimization of vehicle performance and provides a cost-efficient solution with the potential to enable use of a common side airbag design for the global market. The disclosed side airbag has an inflator, a main inflatable chamber disposed for contact with the side arm of the vehicle occupant when inflated, and a separate laterally extending thoracic chamber in metered fluid communication with the main inflatable chamber of the side airbag extending laterally into the passenger compartment and disposed for contact with the lower thoracic region of the vehicle occupant below the occupant's side arm when inflated. Thus, the side airbag engages both the occupant's side arm and lower thoracic region when inflated. The laterally extending thoracic chamber, situated below the occupant's arm, allows essentially simultaneous side airbag engagement with the occupant's upper arm, particularly the shoulder, and the lower thorax. The laterally extending thoracic chamber thus achieves maximal occupant body side coverage during the entire impact event. By maximizing the area upon which the side airbag imparts its load on the occupant, the side airbag is able to absorb more impact energy. The laterally extending thoracic chamber may thereby be designed to simultaneously optimize compliance with FMVSS 214 and other side impact crashworthiness testing protocols by metering fluid communication with the main inflation chamber of the side airbag.
Moreover, the side airbag can be configured so that the inflator inflates the main inflatable chamber at a first predetermined rate of pressure increase and an internal vent between the main inflatable chamber and the laterally extending thoracic chamber inflates the laterally extending thoracic chamber at a second predetermined rate of pressure increase. Thus, the laterally extending thoracic chamber can be made “soft” to accommodate the more vulnerable load case and still stiff enough to absorb enough energy from more severe load cases. In addition, the stiffness of the laterally extending thoracic chamber can be readily engineered to be different from the main chamber, thereby providing opportunities to optimize the performance of the side airbag system from one market to another.